1. Field of the Invention
The present invention relates to a paper feeding device for a variety of image recording apparatus such as copying machines including electrophotographic ones, printers for computer output, or light printers and, more particularly, to a recording paper feeding device with a paper position regulating member, which device can contain a large number of sheets of recording paper supplied and can feed them one by one to a recording unit.
2. Description of the Prior Art
Each image recording apparatus adopts the so-called "cassette type paper feeding system" when various kinds of sheet paper such as ordinary paper, printing paper, photosensitive paper, pressure-sensitive paper, heat-sensitive paper, electrostatic recording paper, transfer paper, or recording sheets of synthetic resin are to be fed to the paper feeding conveyor unit of the recording apparatus body. In the cassette type paper feeding system, the cut paper is contained in the paper feeding cassette, and the cassette receptacle of the apparatus body is charged with the paper feeding cassette so that the cut paper may be fed.
This kind of paper feeding cassette is usually small-sized to have its content limited. In the recording apparatus using a great number of sheets of recording paper and capable of recording at a high speed, the paper feeding cassette raises a defect that the recording apparatus has to be frequently supplied with new recording paper.
In order to cope with the rise in the operating efficiency of the high-speed recording apparatus of the above type in recent years, there has been proposed a paper feeding device which has its efficiency increased by adding a paper feeding stacker having a capacity as large as 1,000 to 2,000 sheets to the paper feeding conveyor unit of the recording apparatus body and by letting off the recording paper generally horizontally by lifting means and paper feeding means disposed at the side of that paper feeding stacker so that a great number of sheets of recording paper may be supplied and conveyed for a long time.
FIG. 8 shows the paper conveyor system of a reproducing machine or the like, which is equipped with a paper feeding stacker of such high capacity (as disclosed in Japanese Patent Publication No. 11663/1985).
In FIG. 8, reference numeral 1 denotes a paper feeding stacker of high capacity for containing a great number of, e.g., 1,000 to 3,000 sheets of paper, and numeral 2 denotes an overlying paper feeding cassette for containing 500 to 1,000 sheets of paper. The sheets of paper are let off one by one from the upper or lower paper feeding unit by a paper feeding roller 3A or 3B. The paper thus let off is then held under pressure between synchronizing rollers 4 to proceed in synchronism with the rotations of a photosensitive drum 5. After this, a toner image is transferred by a transfer electrode 6 to the proceeding paper, which is then delivered to a fixing device 7. In this device 7, the toner on the paper is heated to melt so that it is fixed to the paper. After this, the paper is conveyed by a conveyor belt 8 selectively to a tray 9, a sorter 10 or a both-side copying apparatus (although not shown in the drawing) so that it is discharged to the outside of the body of the copying machine.
The aforementioned large-capacity paper feeding stacker is constructed of lifting means 11, a paper container guide member 12 and a paper container 13. This paper container 13 is equipped inside of its casing with a pair of fixed paper sheaf side regulating members (although not shown in the drawing), a fixed paper front limiting member 14, a fixed paper rear regulating member 15, and a liftable paper sheaf backing plate 16 carrying a sheaf of paper and made movable up and down by the lifting action of the lifting means 11.
The aforementioned paper rear regulating member 15 is a screen or like member anchored at the bottom of the casing of the paper container 13 and having its upper end portion extending to the level of the paper feeding surface of the paper feeding roller 3A.
As the paper feed is started so that the paper sheafs are fed one by one from its uppermost paper, the sheaf has its paper decreased gradually. However, the backing plate 16 is lifted by the lifting means 11, and this lift is so controlled by detecting means that the uppermost level of the paper sheaf may always be maintained at a predetermined paper feed plane.
Here, the leading end portion of the uppermost of the paper sheaf has its level regulated by the paper feeding roller 3A or a separating pawl (although not shown in the drawing). Since, however, the level of the remaining portion of the uppermost part of the paper is not regulated in the least, the uppermost paper may be turned over, pushed back by the paper feeding roller 3A, or advanced obliquely by the oneside feed of the paper feeding roller 3A. As a result, the uppermost paper may ride over the upper end of the paper rear regulating member 15, and the paper sheaf may have uneven rear edges to have sheaf fall to pieces still the worse.
This paper unevenness will invite a deteriorated feed (e.g., no feed or oblique feed) of the paper to cause an abnormal reproduction.